Patients suffering from orthopedic injuries, deformities, or degenerative diseases often require surgery to stabilize an internal structure, promote healing and/or relieve pain. In the spinal field, surgeries to correct spinal abnormalities often involve positioning one or more elongate stabilization elements such as rods, plates or other types of elongate members along a portion of the spinal column, and anchoring each of the elongate stabilization elements to two or more vertebrae via screws, hooks or other types of bone anchors. Prior to anchoring the elongate stabilization element to the spinal column, the surgeon may need to measure the distance between the bone anchors or between two reference locations along the spinal column in order to determine the appropriate length of the elongate stabilization element. In some instances, the bone anchors may be arranged at varying angular orientations, thereby presenting difficulties in accurately measuring the distance between the bone anchors to provide a properly sized elongate stabilization element having a length sufficient for coupling to the bone anchors.
Thus, there is a need for an improved medical instrument that can accurately measure the distance between bone anchors or between two reference locations to determine the appropriate length of an elongate stabilization element to be subsequently coupled to the bone anchors.